Middle English muk, perhaps from Old English -moc; akin to Old Norse myki dung
Date:
13th century
1: soft moist farmyard manure2: slimy dirt or filth3 a: defamatory remarks or writingsb:rubbish, nonsense<mindless muck>4 a
(1): dark highly organic soil
(2):mire, mudb: something resembling muck :gunk5: material removed in the process of excavating or mining